Even in polluted cities, it is still better to bike and walk

Like Elon Musk and Tesla, we have been worrying a lot lately about particulate emissions. In a recent story about emissions in bike lanes, the study author noted that cyclists “tend to have higher breathing rates than other pedestrians, so whatever they’re inhaling is going deeper into their lungs.” Is all that heavy breathing going to compromise cyclists’ health?

Apparently not. A new study from the University of Cambridge led by Marko Tainio asked Can air pollution negate the health benefits of cycling and walking? It found that it takes a lot of pollution to outweigh the benefits of biking and walking. This is a sort of good news/ bad news story; We don't want anyone to accept the idea that particulate pollution is OK, but on the other hand, it is nice to know that it is probably not killing us as quickly as we worried it might be, and that it shouldn't scare us off cycling or walking.

Researchers from CEDAR, a partnership between the Universities of Cambridge and East Anglia, and the Medical Research Council, used computer simulations to compare the risks and benefits for different levels of intensity and duration of active travel and of air pollution in different locations around the world, using information from international epidemiological studies and meta-analyses.

The worldwide urban background level of fine particulate matter (PM2.5) is 22 micrograms per cubic meter (22 µg/m3) and apparently even at the most extreme levels of active travel, the benefits far outweigh the risk. (check your own city here; at time of this writing Toronto is 42, New York City is 13, San Francisco is 38 and London is 66). At 100 µg/m3 the harm outweighs the benefits after an hour and a half of riding, ten hours of walking. Dr. Tainio concludes:

Our model indicates that in London health benefits of active travel always outweigh the risk from pollution. Even in Delhi, one of the most polluted cities in the world -- with pollution levels ten times those in London - people would need to cycle over five hours per week before the pollution risks outweigh the health benefits.

This doesn’t mean we can all forgive Volkswagen and stop worrying about pollution; as another of the study authors notes, “It provides further support for investment in infrastructure to get people out of their cars and onto their feet or their bikes - which can itself reduce pollution levels at the same time as supporting physical activity.”